Light sources emit light for desired applications, but they also emit energy in the form of heat that may be undesirable. For example, a light source may include an electrodeless high-intensity discharge (“HID”) lamp that may reach temperatures of 800° C. The temperature may be increased in systems that use an optic in conjunction with the light source. For example, in many systems it is typical to place an optic over the light source so that the optic can direct and concentrate the light. In such systems the optic typically has a chamber that is dimensioned to receive the light source. When the optic is mounted over the light source, the chamber may become very hot due to the heat energy released by the light source. The conditions inside the chamber are the ambient conditions for the light source, and the ambient conditions may greatly affect either the light source or the optic. For example, the light source may become damaged by excessive temperatures or the restrike time (the time it takes for a light source to turn on after it is turned off) may become unacceptably long. Some optics are made of a material with a melting temperature of 140° C., so the optic may melt or burn if the ambient conditions are very hot.
Thus, it may be necessary to reduce or remove the undesirable heat energy from the light source and/or the chamber (if an optic is used). One solution, particularly for electrodeless HID lamps, was simply to position the optic further away from the light source. But these systems were undesirable, because they required large optics that were expensive, heavy, and generally difficult to manage.
Another solution is to use heat sinks to transfer heat from the light sources, but such heat sinks standing alone are typically ineffective at reducing the temperature inside the chamber (the ambient conditions). Additionally, heat sinks may present certain design problems. Specifically, heat sinks are often finned structures that use simple conduction to remove heat. In such systems it is important to minimize the separation distance between the light source and the heat sink, often referred to as the thermal path. As the thermal path increases, the thermal transfer efficiency decreases. But minimizing the thermal path may cause significant practical limitations to the design of the light source and surrounding systems.
An active cooling system may help reduce the limitations caused by conventional heat sinks that use conduction. Specifically, an active cooling system uses a moving coolant (whether liquid or gas) as the carrier between the light source and the heat sink. The thermal transfer efficiency in active cooling systems is governed by the mass flow rate of the coolant and the heat capacity of the coolant. Thus, active cooling systems may be preferred over simple conduction systems because the thermal transfer efficiency is not dependent upon the length of the thermal path. But such known active cooling systems only transfer the coolant outside of the optic. These systems did not transfer the coolant in the chamber created between the optic and the light source. Thus, the temperature inside the chamber (the ambient conditions of the light source) remains high in these known active cooling systems.
Thus, there is a need to provide an active cooling system to adequately reduce the temperature of the ambient conditions of the light source.